In prior art rotating machinery designs (e.g., liquid rocket engine turbopumps), rolling-element bearings provide radial and axial support of a rotating shaft (referred to as the "rotor") assembly. See FIG. 1. In these designs, a single ball bearing or a pair of preloaded angular contact ball bearings 105 is mounted to the shaft to provide axial thrust capabilities and to control the rotor 135 axial position at low operating speeds. As rotor speed increases, sufficient pressure is provided by the pump to the balance piston cavity 120 to react all of the forces acting on the rotor and to control the rotor axial position within the balance piston position controls (high pressure orifice 125 and low pressure orifice 130). The locations of the ball bearing axial stops, 110 and 115, are selected to prevent axial contact between rotating and stationary parts while at low shaft speed but far enough apart to permit significant rotor axial travel to take advantage of the maximum load capacity of balance piston systems at the higher operating speeds.
Hydrostatic bearings, which use pressurized fluid films to radially support the rotating assembly, are a potentially lower life-cycle cost alternative to conventional rolling element bearings for high speed, long life turbo machines. Unlike rolling-element bearings, radial hydrostatic bearings provide no axial rotor support. Because of this, a way of controlling the start-up and shut-down (i.e., transient) axial thrust is required. One method of controlling transient axial thrust uses a ball bearing whose outer race is mounted to the bearing support 140 but whose inner race is not mounted on the shaft, and is only axially engaged with the rotor 135 during start-up and shut-down. At operating speed, the balance piston controls the axial position of the shaft. The axial stops 110, 115 are located such that the shaft does not contact the axial faces of the bearing once the balance piston controls the shaft position but prevent rubbing of the balance piston high and low pressure orifices 125 and 130 while operating at low speed. This, in tun, requires that the rotor axial stops 110, 115, be farther apart at operating speeds than during either start-up or shut-down. One means of accomplishing this is through a rotating clutch mechanism.
As is well known to those of ordinary skill, the purpose of a rotating clutch is to transmit torque through axial contact and, generally speaking, is intended to engage and disengage selectively, either actively (for example, by pushing in the clutch pedal of an automobile) or passively (for example, in response to specific events such as increases in engine speed).
The invention relates to a passive rotational clutch mechanism that utilizes the change of centripetal force of a rotating shaft to produce the axial clutching against the bearing, i.e., a retracting or disengaging motion as speed increases and an engaging motion as speed decreases.